U.S. patent number 3,879,491 [Application Number 05/417,990] was granted by the patent office on 1975-04-22 for toughened thermoplastics containing polydiorganosiloxanes.
This patent grant is currently assigned to Dow Corning Corporation. Invention is credited to Sarah E. Lindsey, John C. Saam.
United States Patent |
3,879,491 |
Lindsey , et al. |
April 22, 1975 |
Toughened thermoplastics containing polydiorganosiloxanes
Abstract
A continuous matrix of a thermoplastic from styrene,
methylmethacrylate, ring substituted alkyl styrenes and copolymers
thereof having dispersed therein gelled particles of thermoplastic
and a polydiorganosiloxane gum having from 15 to 25 mol percent
diorganosiloxane units containing vinyl or allyl radicals provides
a toughened thermoplastic prepared by polymerizing the
thermoplastic monomers having the polydiorganosiloxane gum
dispersed therein with agitation at 35.degree.C. to 200.degree.C.
by free radical means.
Inventors: |
Lindsey; Sarah E. (Midland,
MI), Saam; John C. (Midland, MI) |
Assignee: |
Dow Corning Corporation
(Midland, MI)
|
Family
ID: |
26939975 |
Appl.
No.: |
05/417,990 |
Filed: |
November 21, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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249327 |
May 1, 1972 |
|
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Current U.S.
Class: |
525/479; 525/104;
525/106 |
Current CPC
Class: |
C08F
283/124 (20130101) |
Current International
Class: |
C08F
283/12 (20060101); C08F 283/00 (20060101); C08f
033/08 (); C08g 047/10 () |
Field of
Search: |
;260/827 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Briggs, Sr.; Wilbert J.
Attorney, Agent or Firm: Borrousch; Roger H.
Parent Case Text
This is a continuation-in-part of application Ser. No. 249,327,
filed May 1, 1972, and now abandoned.
Claims
1. A toughened thermoplastic composition having values for notched
Izod impact strengths in foot pounds per inch of notch wherein the
notch is 45 degrees and 0.1 inch deep at least 35 percent greater
than unmodified thermoplastic wherein the thermoplastic in the
toughened thermoplastic composition is the same as the unmodified
thermoplastic, consisting essentially of a continuous matrix of a
thermoplastic wherein the unpolymerized monomeric compounds were
selected from the group consisting of styrene, methylmethacrylate,
ring substituted alkyl styrenes, mixtures thereof, and mixtures of
at least one monomer selected from the group consisting of styrene,
methylmethacrylate and ring substituted alkyl styrenes with at
least one monomer selected from the group consisting of
acrylonitrile, alpha-methylstyrene, maleic anhydride,
methacrylonitrile, acrylic acid, vinyl halides and vinylidene
halides, having dispersed therein gelled particles which have a
range of diameters from 0.05 micron to 200 microns inclusive, where
the geometric mean diameter is from 0.3 micron to 20 microns
inclusive, said gelled particles consisting essentially of
polydiorganosiloxane of the formula X[(R.sub.2
SiO).sub.m(RR"SiO).sub.1.sub.-m ].sub.x X' having polymeric species
derived from the above defined monomeric compounds grafted thereto
through the R" radical, where R is a monovalent radical having a
maximum of 18 carbon atoms and selected from the group consisting
of hydrogen atom, alkyl, haloalkyl, aryl, haloaryl and aralkyl,
wherein at least 50 percent of the R radicals are lower alkyl
radicals having less than 3 carbon atoms, X is an endblocking group
selected from the group consisting of R'R.sub.2 SiO-- and HO--, X'
is an endblocking group selected from the group consisting of
R'R.sub.2 Si-- and H--, R' is a monovalent radical selected from
the group consisting of R radicals, vinyl and allyl, R" is vinyl or
allyl, m and 1-m represent the mole ratio of each type of
diorganosiloxane unit in the polydiorganosiloxane, respectively,
and m has a value from 0.75 to 0.85 inclusive, x represents the
total number of diorganosiloxane units in the polydiorganosiloxane
and has a value sufficient to provide a Williams plasticity of at
least 0.060 inch as determined on the unreacted
polydiorganosiloxane, the polydiorganosiloxane being present in an
amount of from 1 to 15 weight percent based on the total combined
weight of the thermoplastic and the polydiorganosiloxane, said
toughened thermoplastic composition being prepared by polymerizing
with agitation at 35.degree.C. to 200.degree.C. by free radical
means, the monomeric compounds described above in which the
unreacted
2. The toughened thermoplastic composition according to claim 1 in
which R is methyl, R" is vinyl and the Williams plasticity is from
0.060 to 0.150
3. The toughened thermoplastic composition according to claim 1 in
which
4. The toughened thermoplastic composition according to claim 2 in
which
5. The toughened thermoplastic composition according to claim 1 in
which
6. The toughened thermoplastic composition according to claim 2 in
which the polydiorganosiloxane is present in an amount of from 1 to
10 weight
7. In a method for polymerizing monomeric compounds selected from
the group consisting of styrene, methylmethacrylate, ring
substituted alkyl styrenes, mixtures thereof, and mixtures of at
least one monomer selected from the group consisting of styrene,
methylmethacrylate and ring substituted alkyl styrenes with at
least one monomer selected from the group consisting of
acrylonitrile, alpha-methylstyrene, maleic anhydride,
methacrylonitrile, acrylic acid, vinyl halides and vinylidene
halides, comprising agitating the monomeric compounds and
polymerizing at 35.degree.C. to 200.degree.C. by free radical
means, whereby a thermoplastic is obtained, the improvement
consisting essentially of dispersing in the agitating monomeric
compound prior to polymerization initiation a polydiorganosiloxane
in the amount of from 1 to 15 percent by weight based on the
combined weight of the monomeric compound and the
polydiorganosiloxane and of the formula X[(R.sub.2 SiO).sub.m
(RR"SiO).sub.1.sub.-m ].sub.x X' wherein R is a monovalent radical
having a maximum of 18 carbon atoms and selected from the group
consisting of hydrogen atom, alkyl, haloalkyl, aryl, haloaryl and
aralkyl, wherein at least 50 percent of the R radicals are lower
alkyl radicals having less than 3 carbon atoms, X is an endblocking
group selected from the group consisting of R'R.sub.2 SiO-- and
HO--, X' is an endblocking group selected from the group consisting
of R'R.sub.2 Si-- and H--, R' is a monovalent radical selected from
the group consisting of R radicals, vinyl and allyl, R" is vinyl or
allyl, m and 1- m represent the mole ratio of each type of
diorganosiloxane unit in the polydiorganosiloxane, respectively,
and m has a value from 0.75 to 0.85 inclusive, x represents the
total number of diorganosiloxane units in the polydiorganosiloxane
and has a value sufficient to provide a Williams plasticity of at
least 0.060 inch, whereby the thermoplastic composition obtained is
toughened to the extent of having values for a notched Izod impact
strength in foot pounds per inch of notch wherein the notch is
45.degree. and 0.1 inch deep at least 35 percent greater than
unmodified thermoplastic wherein the thermoplastic in the toughened
thermoplastic composition is the same as
8. The method in accordance with claim 7 in which the monomeric
compound is styrene, R is methyl, R" is vinyl and the Williams
plasticity is from 0.060 to 0.150 inch.
Description
This invention relates to a toughened thermoplastic.
Many thermoplastics are inexpensive and have useful properties.
However, the thermoplastics also have shortcomings which distract
from their use in even broader applications and which add to their
manufacturing cost. Some of these properties which need improvement
include handling properties, impact strength, weatherability,
surface properties and low temperature properties, among others.
For example, the need for improved impact strength is apparent to
any parent who has purchased a toy for his child made from one of
these thermoplastics. Often these thermoplastics toys in normal
play will break and leave jagged edges exposed on which the child
can be seriously injured to say nothing of the loss of the toy. If
toys made from these thermoplastics can be readily broken by a
child, it is apparent that these thermoplastic materials will have
limited value in many other areas, such as construction of
articles, in automobiles, building and the like, unless the
thermoplastic can be toughened.
Toughening of commercial glassy thermoplastics by including organic
rubbers as fine micro-dispersions is a well known and important
step toward providing these materials with increased resistance to
mechanical shock. As is shown in U.S. Pat. No. 3,442,851, rubbery
polymer can be used to contribute to the impact strength of the
finished material, however, one sacrifices the flexural properties
by doing so and a balance between impact strength and flexural
properties is sought to obtain the maximum impact strength with the
least effect on the flexural strength.
It is also known from U.S. Pat. No. 3,239,579, that the alkenyl
aromatic resins can be blended with diorganopolysiloxane elastomers
to provide a composition which is water resistant, possesses
excellent electrical properties, are resistant to deterioration
upon aging in the presence of air, light, heat or oxygen and can
form articles having good mechanical properties such as impact
strength and percent elongation. The diorganopolysiloxane
elastomers taught by this patent, however, are limited to those
containing methyl and phenyl radicals bonded to the silicon atoms.
The compositions are prepared by blending which is an added step in
the process and the tensile strength and impact strength both
decrease on increasing amount of the silicone rubber.
The present invention has added advantages over the prior art
methods for increasing the impact strength in that the blending
step is avoided and the increased impact strength obtained does not
sacrifice the tensile strength as much as in the prior art. It is
therefore an object of this invention to provide a toughened glassy
thermoplastic with an improved property profile without
significantly altering the processing now being used to make the
glassy thermoplastics. This object and others will become more
apparent from the following detailed description of the present
invention.
This invention relates to a toughened thermoplastic composition
having values for notched Izod impact strengths in foot pounds per
inch of notch wherein the notch is 45.degree. and 0.1 inch deep of
at least 35 percent greater than unmodified thermoplastic wherein
the thermoplastic in the toughened thermoplastic composition is the
same as the unmodified thermoplastic, consisting essentially of a
continuous matrix of a thermoplastic wherein the unpolymerized
monomeric compounds were selected from the group consisting of
styrene, methylmethacrylate, ring substituted alkyl styrenes,
mixtures thereof, and mixtures of at least one monomer selected
from the group consisting of styrene, methylmethacrylate and ring
substituted alkyl styrenes with at least one monomer selected from
the group consisting of acrylonitrile, alpha-methylstyrene, maleic
anhydride, methacrylonitrile, acrylic acid, vinyl halides and
vinylidene halides, having dispersed therein gelled particles which
have a range of diameters from 0.05 micron to 200 microns
inclusive, where the geometric mean diameter is from 0.3 micron to
20 microns inclusive, said gelled particles consisting essentially
of polydiorganosiloxane of the formula X[R.sub.2 SiO).sub.m
(RR"SiO).sub.1.sub.-m ].sub.x X' having polymeric species derived
from the above defined monomeric compounds grafted thereto through
the R" radical, where R is a monovalent radical having a maximum of
18 carbon atoms and selected from the group consisting of hydrogen
atom, alkyl, haloalkyl, aryl, haloaryl and aralkyl, wherein at
least 50 percent of the R radicals are lower alkyl radicals having
less than 3 carbon atoms, X is an endblocking group selected from
the group consisting of R'R.sub.2 SiO-- and HO--, X' is an
endblocking group selected from the group consisting of R'R.sub.2
Si-- and H--, R' is a monovalent radical selected from the group
consisting of R radicals, vinyl and allyl, R" is vinyl or allyl, m
and 1-m represent the mole ratio of each type of diorganosiloxane
unit in the polydiorganosiloxane, respectively, and m has a value
from 0.75 to 0.85 inclusive, x represents the total number of
diorganosiloxane units in the polydiorganosiloxane and has a value
sufficient to provide a Williams plasticity of at least 0.060 inch
as determined on the unreacted polydiorganosiloxane, the
polydiorganosiloxane being present in an amount of from 1 to 15
weight percent based on the total combined weight of the
thermoplastic and the polydiorganosiloxane, said toughened
thermoplastic composition being prepared by polymerizing with
agitation at 35.degree.C. to 200.degree.C. by free radical means,
the monomeric compounds described above in which the unreacted
polydiorganosiloxane is dispersed.
This invention also relates to an improvement in a method for
polymerizing monomeric compounds selected from the group consisting
of styrene, methylmethacrylate, ring substituted alkyl styrenes,
mixtures thereof, and mixtures of at least one monomer selected
from the group consisting of styrene, methylmethacrylate and ring
substituted alkyl styrenes with at least one monomer selected from
the group consisting of acrylonitrile, alpha-methylstyrene, maleic
anhydride, methacrylonitrile, acrylic acid, vinyl halides and
vinylidene halides, comprising agitating the monomeric compounds
and polymerizing at 35.degree.C. to 200.degree.C. by free radical
means, whereby a thermoplastic is obtained, the improvement
consisting essentially of dispersing in the agitating monomeric
compound prior to polymerization initiation a polydiorganosiloxane
in the amount of from 1 to 15 percent by weight based on the
combined weight of the monomeric compound and the
polydiorganosiloxane and of the formula X[(R.sub.2 SiO).sub.m
(RR"SiO).sub.1.sub.-m ].sub.x X' wherein R is a monovalent radical
having a maximum of 18 carbon atoms and selected from the group
consisting of hydrogen atom, alkyl, haloalkyl, aryl, haloaryl and
aralkyl, wherein at least 50 percent of the R radicals are lower
alkyl radicals having less than 3 carbon atoms, X is an endblocking
group selected from the group consisting of R'R.sub.2 SiO-- and
HO--, X' is an endblocking group selected from the group consisting
of R'R.sub.2 Si-- and H--, R' is a monovalent radical selected from
the group consisting of R radicals, vinyl and allyl, R" is vinyl or
allyl, m and 1-m represent the mole ratio of each type of
diorganosiloxane unit in the polydiorganosiloxane, respectively,
and m has a value from 0.75 to 0.85 inclusive, x represents the
total number of diorganosiloxane units in the polydiorganosiloxane
and has a value sufficient to provide a Williams plasticity of at
least 0.060 inch, whereby the thermoplastic composition obtained is
toughened to the extent of having values for a notched Izod impact
strength in foot pounds per inch of notch wherein the notch is
45.degree. and 0.1 inch deep at least 35 percent greater than
unmodified thermoplastic wherein the thermoplastic in the toughened
thermoplastic composition is the same as the unmodified
thermoplastic.
The methods for preparing the toughened thermoplastic compositions
of the present invention are essentially those methods as known to
the art for the preparation of the polymeric compositions per se.
For example, toughened polystyrene compositions of this invention
can be prepared by essentially the same methods as are now used
commercially to prepare polystyrene. The glassy thermoplastics of
the present invention are prepared by polymerizing the monomeric
compounds by free radical means at 35.degree.C. to 200.degree.C.
while agitating the mixture. The difference between the prior art
methods and the method of the present invention is that the
monomeric compounds have the hereindefined polydiorganosiloxane
dispersed therein before the polymerization of the monomeric
compounds is initiated. The product resulting from this method is a
toughened thermoplastic composition having an improved property
profile.
The preferred method for preparing the toughened thermoplastic
compositions of the present invention is to dissolve or disperse
the polydiorganosiloxane in the polymerizable monomers which have
any inhibitors removed by agitating the mixture until the
polydiorganosiloxane is thoroughly dispersed. The
polydiorganosiloxane mixes with the monomeric compounds
sufficiently well to form a homogeneous distribution of the
polydiorganosiloxane in the monomeric compounds and the resulting
mixture can be termed a solution or dispersion. The mixture does
not separate into layers. The polydiorganosiloxane can be readily
dispersed in the agitating polymerizable monomer. The
polydiorganosiloxane is added to the agitating polymerizable
monomer which can be heated to aid the dispersion or dissolution
and then bulk polymerized by heating to a temperature which is
dependent upon the particular polymerizable monomers. For example,
styrene can be bulk polymerized at 100.degree.C. to 140.degree.C.
after the polydiorganosiloxane is added. The polymerization being
free radical initiated is preferably carried out under an inert
atmosphere such as nitrogen. After the mixture of
polydiorganosiloxane and polymerizable monomer is partly
polymerized and becomes viscous, the polymerizable mass is cooled
to a temperature so that the free radical means can be
introduced.
The free radical means can be any of the known free radical
generators which will function under the reaction conditions. One
class of free radical generators are the peroxides,
di(tertiary-butylperphthalate), tertiary-butylpercaprylate,
tertiary-butylperbenzoate, di-acetylperoxide, acetylbenzoyl
peroxide, dipropionyl peroxide, dilauryoyl peroxide, dimethyl
peroxide, diethyl peroxide, dipropyl peroxide, tetralin peroxide,
cyclohexane peroxide, acetone peroxide, cyclohexyl hydroperoxide,
cumeme hydroperoxide, tertiary-butyl hydroperoxide, methyl
cyclohexyl hydroperoxide; another class is the hydrazine
derivatives such as hydrazine hydrochloride, hydrazine sulfate,
dibenzoylhydrazine, diacetylhydrazine and trimethylhydrazinium
iodide; amine oxides such as, pyridine oxide, trimethylamine oxide,
dimethylaniline oxide; alkali metal and ammonium persulfates,
perborates and percarbonates; ketaldones; azines such as
benzalazine, heptaldazine and diphenylketazine; oximes such as
d-camphor oxime, acetone oxime, alpha-benzil dioxime,
butyraldoxime, alpha-benzoin oxime, oxime and dimethylglyozime;
hydrazones such as benzaldehyde phenylhydrazone, phenylhydrazones
of cyclohexanone, cyclopentanone; semicarbazones such as
semicarbazones of acetone, methylethyl ketone, diethyl ketone,
biacetyl, cyclopentanone, cyclohexanone, acetophenone,
propiophenone, camphor and benzophenone; Schiff's bases such as
benzalaniline, benzal-p-toluidine, benzal-o-toluidine, benzaldehyde
derivatives of methylamine, ethylamine and heptylamine; anils and
analogous compounds of other amines, such as acetaldehyde anil,
isobutyraldehyde anil, heptaldehyde anil; azo-bis-iosbutyronitrile,
the reaction products of organometallics such as cadmium alkyl,
zinc alkyls, tetraethyl lead and aluminum alkyls with oxygen and
high energy ionizing radiation.
After the free radical generator is introduced, the dispersion is
suspended in water with the aid of a suspending agent such as
sodium carboxymethylcellulose, gum agar, hydroxypropyl
methylcellulose, carboxy methylcellulose, methyl cellulose,
colloidal silica and colloidal clays. The suspension is agitated to
provide droplets of the organic phase, such as about one sixteenth
to one eighth inch in diameter. The suspension is then brought to
polymerization conditions and the polymerization completed. The
resulting product is obtained by removing any unreacted monomer,
separating the product which is in bead form by filtering, for
example, washing and drying to obtain the product.
The above method describes a bulk type polymerization which is
carried out in a suspension. Other methods of polymerization can
also be used such as emulsion polymerization and mass
polymerization. The known types and conditions for the
polymerizations can be used as long as the polydiorganosiloxane is
present during the polymerization of the monomeric compounds, the
polymerization is by free radical means and the polymerizing medium
is agitated to insure thorough distribution of the
polydiorganosiloxane.
The polymerizable monomeric compounds for the purpose of this
invention include those whose homopolymers and copolymers are
glassy thermoplastics under ambient conditions. When single
monomers are polymerized, they can be styrene, methylmethacrylate
or ring substituted alkyl styrenes such as ortho-vinyltoluene,
meta-vinyltoluene, para-vinyltoluene, vinylxylene and
isopropylvinylbenzene. The above monomers can be copolymerized such
as styrene and methylmethacrylate, styrene and vinylxylene and the
like. Also other monomers can be copolymerized with one or more of
the above monomers. The other monomers include acrylonitrile,
alpha-methylstyrene, maleic anhydride, methacrylonitrile, acrylic
acid, vinyl halides and vinylidene halides wherein at least one of
these monomers is polymerized with at least one monomer of styrene,
methylmethacrylate or a ring substituted alkyl styrene. It is
within the scope of the present invention to include minor amounts
of other free radical polymerizable monomers, however, these
monomers should be present in amounts so that the resulting
compositions are still glassy thermoplastics at ambient conditions.
The monomers in minor or trace amounts can be, for example,
divinylbenzene, butadiene, isoprene, alkylalkacrylates other than
methylmethacrylate and alkylacrylates.
The polydiorganosiloxanes used in the present invention are those
having a formula X[(R.sub.2 SiO).sub.m (RR"SiO).sub.1.sub.-m
].sub.x X' wherein R is a monovalent radical haing a maximum of 18
carbon atoms including a hydrogen atom; an alkyl radical such as
methyl, ethyl, propyl, isopropyl, octyl, cyclohexyl, cyclopentyl,
dodecyl and octadecyl; haloalkyl such as 3-chloropropyl,
3,3,3-trifluoropropyl, perfluoroalkylethyl radicals, chloromethyl
and bromooctadecyl; aryl radicals such as phenyl, tolyl, xylyl,
3-ethylphenyl, xenyl, naphthyl, anthracyl and
3,4-methylethylphenyl; haloaryl radicals such as
2,4-dichlorophenyl, dibromoxenyl, alpha,alpha,alpha-trifluorotolyl
and iodonaphthyl and aralkyl radicals such as benzyl,
2-phenyloctyl, 2-phenylethyl, 2-phenylpropyl and
3-methyl-2-(4-isopropylphenyl)heptyl; X is an endblocking group of
R'R.sub.2 SiO-- or HO-- (hydroxyl); X' is an endblocking group of
R'R.sub.2 Si- or H(hydroxy); R' is an R radical, vinyl or allyl and
R" is vinyl or allyl. At least 50 percent of the R radicals are
lower alkyl radicals having less than 3 carbon atoms and include
methyl and ethyl, preferably methyl. It is also preferred that the
R radicals are at least 90 percent lower alkyl.
In the formula for the polydiorganosiloxane, m and 1-m represent
the mole ratio of each type of diorganosiloxane unit in the
polydiorganosiloxane. Thus, m represents the mole ratio of R.sub.2
SiO units in the polydiorganosiloxane and 1-m represents the mole
ratio of RR" SiO units in the polydiorganosiloxane. For the present
invention, m has a value from 0.75 to 0.85 inclusive and 1-m would
have value from 0.15 to 0.25. When m is either more than 0.85 or
less than 0.75, the impact strength decreases significantly. Also,
in the above formula for the polydiorganosiloxane x represents the
total number of diorganosiloxane units in the polydiorganosiloxane
and has a value sufficient to provide a Williams plasticity of at
least 0.060 inch, preferably 0.060 to 0.0150 inch. The
polydiorganosiloxanes can be prepared by methods known in the art
such as by polymerizing a mixture of the cyclic (R.sub.2 SiO).sub.y
and cyclic (RR"SiO).sub.y where y is 3 or 4 with a basic catalyst
such as potassium silanolate. The polydiorganosiloxanes can be
random copolymers, block copolymers and any of the possible forms
which exist between the true random copolymer and true block
copolymer. The polydiorganosiloxane can be hydroxyl or
triorganosilyl endblocked. Because the amount of endblocking is
small in these high molecular weight polymers, it has little or no
effect on polydiorganosiloxane.
The amount of polydiorganosiloxane can be from 1 to 15 weight
percent based on the combined weight of the polydiorganosiloxane
and the monomeric compound, preferably, the amount is from 1 to 10
weight percent. Amounts of polydiorganosiloxane greater than 15
weight percent tend to provide compositions which are something
less than glassy thermoplastics. Amounts of polydiorganosiloxane
less than 1 weight percent do not significantly improve the impact
strength.
The products from the method described above are toughened
thermoplastic compositions as observed from the values obtained for
notched Izod impact strengths as determined by ASTM-D256-56
procedure wherein the values are in 45.degree. 0.1 inch notched
foot pounds per inch. For the purposes of the present invention,
those impact strength values for the toughened thermoplastic
compositions which are at least 35 percent greater than those
impact strength values for the thermoplastic compositions without
the polydiorganosiloxane modification are considered significant
improvement in the toughness or impact strength to be within the
scope of this invention. The impact values compared are for the
same thermoplastic systems wherein one contains the
polydiorganosiloxane and the other does not. Impact strength values
between compared thermoplastics with and without the
polydiorganosiloxane which are less than 35 percent greater for the
with than the without are considered insignificant improvement for
the purposes of this invention.
The improvements in impact strength for the toughened thermoplastic
compositions of this invention are obtainable with smaller amounts
of the polydiorganosiloxane compared to the organic rubber
previously used without as much decrease in the ultimate tensile
strength.
The toughened thermoplastic compositions of this invention are
sufficiently ductile with unidirectional cold rolling to permit
fabrication by cold forming processes. This ability to be cold
rolled is particularly apparent when the original specimens are
injection molded. The brittle-ductile transition for the toughened
thermoplastic compositions are lowered, such as for a toughened
polystyrene composition the brittle-ductile transition is about
-90.degree.C., where this transition was designated as that
temperature where the impact strength falls off precipitously to
brittle failure.
The surface characteristics of the toughened thermoplastic
compositions drastically changed compared to unmodified
thermoplastics. For example, the coefficient of friction for the
toughened polystyrene composition is about one half of the value
for the unmodified polystyrene when 2 weight percent
polydiorganosiloxane is used.
The toughened thermoplastics of the present invention are
significantly more resistant to weathering than thermoplastics
modified with unsaturated organic rubbers. This property would
allow more outside use of the thermoplastics.
The toughened thermplastic compositions of this invention consist
essentially of a continuous matrix of a thermoplastic derived from
the unpolymerized monomers as defined above. The continuous
thermoplastic matrix has dispersed therein gelled particles which
have a range of diameters from 0.05 to 200 microns inclusive where
the geometric means diameter is from 0.3 micron to 20 microns
inclusive. The geometric mean diameter is a mean diameter of the
particle distribution in which 50 percent of the particles are
larger and 50 percent of the particles are smaller than this
geometric mean diameter. The geometric mean diameter can be
determined as set forth in Small Particle Statistics, by G. Herdan,
Elsever Publishing Co., N.Y., 1953 Printing, Chapter, 4, page
43.
The gelled particles consist essentially of the
polydiorganosiloxane as defined herein having polymeric species
derived from the unpolymerized monomeric compounds grafted to the
polydiorganosiloxane through the R" radical of the
polydiorganoxiloxane. Because the polymerization is by free radical
means, some grafting can be expected to be through the methyl or
ethyl radicals as well as other R radicals. Because the vinyl or
allyl radicals are so much more reactive, the grafting for the
purposes of this invention will be said to be through the R"
radicals. These gelled particles are formed during the
polymerization of the dispersion of the polydiorganosiloxane in the
unpolymerized monomeric compounds.
The preferred toughened thermoplastic compositions are the
toughened polystyrene and the toughened styrene-acrylonitrile
copolymers with impact strengths 50 percent greater than the impact
strengths of the unmodified polystyrene and styrene-acrylonitrile
copolymers.
The following examples are presented for illustrative purposes only
and should not be construed as limiting this invention which is
properly delineated in the claims.
EXAMPLE 1
A hydroxyl endblocked polydiorganosiloxane having 18 mole percent
methylvinylsiloxane units and 82 mole percent dimethylsiloxane
units and a Williams plasticity of 0.071 inch in an amount of 36.8
grams was dissolved in 919 grams of styrene from which the
inhibitors were removed. This solution was initially bulk
polymerized by heating to 120.degree.C. for 1.5 hours while being
stirred at 125 r.p.m. The resulting viscous partly polymerized mass
was cooled to 70.degree.C. and then 1.9 grams of benzoyl peroxide
was added followed by the addition of a solution of 16 grams of
sodium carboxymethylcellulose in 3100 ml. of water with an increase
in the rate of stirring so that a suspension of the viscous, partly
polymerized mass formed and provided droplets of approximately
one-eighth inch in diameter in the aqueous medium. This suspension
was stirred and heated at 80.degree.C. for 16 hours after which the
polymerization was essentially complete. The last traces of monomer
were removed by steam distillation. A nearly quantitative yield of
a polydiorganosiloxane modified polystyrene was obtained in the
form of solid beads which were easily filtered and dried.
The Williams plasticity as used herein was determined on a 4.2 gram
sample, for three minutes at room temperature in accordance with
ASTM-D-926-67 procedure.
Sample Preparation: Samples were prepared for mechanical testing by
mixing and shearing 80 grams of thermoplastic composition in a
commercial mixer, a Brabender Plasticorder, at 180.degree.C. for 6
minutes and then compression molding at 170.degree.C. into 70 mil
slabs. The slabs were cut into suitable strips for the Notched Izod
Impact Test (ASTM-D-256-56). Samples were also compression molded
into 2.5 inch by 0.5 inch by 0.5 inch bars for the Notched Izod
Impact Test. The difference in results obtained on samples prepared
by either method was negligible. A 45.degree. 0.1 inch notch was
used for the Notched Izod Impact Test and the results were recorded
in foot-pounds per inch of notch.
Injection molded test pieces were prepared with a 1 reciprocating
screw machine made by Newbury Industries, Model H 130RS. The test
pieces were molded under the following conditions: cycle time of 45
seconds, injection time of 7 seconds, gauge pressure of 650 p.s.i.,
mold temperature of cavity of 100.degree.F., mold temperature of
core of 100.degree.F., rear zone temperature of 440.degree.F.,
front zone temperature of 455.degree.F. and nozzle temperature of
450.degree.F. The injection molded test pieces were a 51/2 inch
test bar, a 51/2 inch flex bar and a 2 inch diameter disc with each
test piece being 0.135 inch thick. The notched Izod impact strength
values for both the compression molded and injection molded samples
had about .+-.10 percent deviation for different samples of the
same material.
The compression molded samples of the polydiorganosiloxane modified
polystyrene prepared above had a notched Izod impact strength of
1.25 foot-pounds per inch of notch and the injection molded samples
had a notched Izod impact strength of 1.36 foot-pounds per inch of
notch. A sample prepared as described above except the
polydiorganosiloxane was left out had a notched Izod impact
strength of 0.38 foot-pounds per inch of notch for compression
molded samples. Thus, the polydiorganosiloxane modified polystyrene
was a toughened thermoplastic composition having approximately 230
percent improvement in notched Izod impact strength compared to the
unmodified polystyrene.
EXAMPLE 2
A. In a manner similar to the procedure of Example 1, 91.9 grams of
a hydroxyl endblocked polydiorganosiloxane having 23 mole percent
methylvinylsiloxane units and 77 mole percent dimethylsiloxane
units and a Williams plasticity of 0.115 inch was mixed with 919
grams of styrene (inhibitor removed) and bulk pre-polymerized at
118.degree. to 120.degree.C. for 1.5 hours, cooled to 50.degree.C.,
and then 1.9 grams of benzoyl peroxide was added followed by a
solution of 20 grams of sodium carboxymethylcellulose in 3100 ml.
of water to form a suspension. The suspension was then polymerized
at 80.degree.C. for 18 hours, steam distilled, filtered and dried
to provide solid beads of polydiorganosiloxane modified
polystyrene. Compression molded samples had a notched Izod impact
strength of 1.55 foot-pounds per inch of notch and injection molded
samples had a notched Izod impact strength of 1.59 foot-pounds per
inch of notch. Thus, the polydiorganosiloxane toughened polystyrene
showed an improvement in notched Izod impact strengths of
approximately 300 percent. This toughened polystyrene contained 10
weight percent polydiorganosiloxane based on the combined weight of
the polydiorganosiloxane and the styrene.
B. A mixture of 24 grams of the polydiorganoxiloxane toughened
polystyrene prepared in A. above was mixed with 56 grams of the
polystyrene prepared in Example 1 (without polydiorganosiloxane).
This mixture was fused and mixed under shear at 190.degree.C. in a
Brabender Plasticorder and then compression molded into test
pieces. The test pieces had a notched Izod impact strength of 0.68
foot-pounds per inch of notch. This blended mixture of a
polydiorganosiloxane toughened polystyrene and polystyrene had a
polydiorganosiloxane content of 3 weight percent based on the
combined weight of the polydiorganosiloxane and polystyrene. This
blended mixture was toughened as shown by an increase in notched
Izod impact strength of about 80 percent. This shows that
polydiorganosiloxane toughened thermoplastic compositions of this
invention can be further blended with additional thermoplastic
while retaining its ability to toughen the final product.
EXAMPLE 3
This example shows the toughening of a styrene-acrylonitrile
copolymer in accordance with the present invention. 18.4 grams of a
hydroxyl endblocked polydiorganosiloxane having 18 mole percent
methylvinylsiloxane units and 82 mole percent dimethylsiloxane
units was dissolved in 643.3 grams of styrene and 275.7 grams of
acrylonitrile. The inhibitors having been removed from each
monomer. To this mixture, 1.9 grams of benzoyl peroxide was added
and the mixture was stirred at 120 r.p.m. at 80.degree. to
85.degree.C. for 1.5 hours. To the resulting partly polymerized
mass, a solution of 18 grams of sodium carboxymethylcellulose in
3100 ml. of water was added and the rate of agitation was
accelerated so as to give a uniform suspension of the partly
polymerized mass. Polymerization was continued in the suspension
for 18 hours at 80.degree. to 85.degree.C. A high yield of
polydiorganosiloxane modified styrene-acrylonitrile copolymeric
thermoplastic composition in the form of beads was obtained. This
thermoplastic composition, containing 2 weight percent of
polydiorganosiloxane, was isolated and fabricated into test samples
as described in Example 1. The notched Izod impact strength of a
compression molded sample was 2.03 foot-pounds per inch of notch.
This impact strength was an improvement of about 400 percent over
an unmodified copolymer of styrene and acrylonitrile.
EXAMPLE 4
A. This example shows the toughening of a
styrene-methylmethacrylate-alpha-methylstyrene terpolymer in
accordance wtih the present invention. 16.08 grams of a hydroxyl
endblocked polydiorganosiloxane having 20 mole percent
methylvinylsiloxane units and 80 mole percent dimethylsiloxane
units and having a Williams plasticity of 0.115 inch was mixed wtih
160.8 grams of styrene, 46 grams of methylmethacrylate and 23 grams
of alpha-methylstyrene and allowed to stand overnight. The mixture
was then placed in a flask under a nitrogen atmosphere, stirred at
about 150 r.p.m.; heated to 120.degree.C. and held at this
temperature for 1.75 hours. The mixture was then cooled below
80.degree.C. and 0.045 gram of benzoyl peroxide added followed by a
solution of 4.5 grams of sodium carboxy methylcellulose in 775
grams of water. The mixture was stirred rapidly to form a
suspension and the temperature increased to 80.degree.C. and
maintained at this temperature for 7 hours. The completed
polymerization mixture was stripped to remove any residual monomers
and a polydiorganosiloxane modified
styrene-methylmethacrylate-alpha-methylstyrene terpolymer was
obtained in the form of beads after filtering, washing with water
and ethanol and drying in a vacuum oven. The beads were then
fabricated into test pieces by massing in a Brabender Plasticorder
at 63 r.p.m., 190.degree.C. for 6 minutes (CAM Head) and then
compression molded at 173.degree.C. The polydiorganosiloxane
modified terpolymer had a notched Izod impact strength of 1.168
foot-pounds per inch of notch.
B. The above procedure of A. was repeated except the
polydiorganosiloxane was left out. The resulting
styrene-methylmethacrylate-alpha-methylstyrene terpolymer had a
notched Izod impact strength of 0.337 foot-pounds per inch of notch
for compression molded samples. Thus, the polydiorganosiloxane
modified terpolymer was toughened to the extent that the impact
strength increased about 250 percent over the unmodified
terpolymer.
EXAMPLE 5
The procedure of Example 2 was repeated except the amount of the
polydiorganosiloxane was varied as shown in Table I. The test
samples prepared were tested in accordance with the ASTM procedures
as follows: tensile strength at break and elongation at break,
ASTM-D-638, run on injection molded samples at a jaw separation
rate of 0.2 inch per minute; flexural strength and flexural modulus
ASTM-790-66, run at a rate of cross head motion of 0.05 inch per
minute; and heat distortion temperature, ASTM-D-648-56 (264 p.s.i.)
on samples annealed for 16 hours at 98.degree.C. The results
obtained were as shown in Table I.
TABLE I
__________________________________________________________________________
Notched Izod Impact Strength ft. lbs/in. of Notch Weight Tensile
Heat Percent Compres- Injec- Strength Elonga- Flexural Flexural
Distortion Static Run Polydiorgano- sion tion At Break tion At
Strength Modulus temper- Coefficient No. siloxane Molded Molded
p.s.i. Break, % p.s.i. p.s.i ature, .degree.C of
__________________________________________________________________________
Friction 1. (STYRON T430)* 0.93 1.0 4050 21 -- -- 91 0.725 2.
(STYRON 686)* 0.32 0.33 5080 4 12.900 534,000 90 0.80 3. 0.0* 0.38
-- -- -- -- -- -- -- 4. 1.0 0.58 0.71 6150 10 13,300 475,000 91
0.70 5. 2.0 0.84 0.99 5250 16 11,900 416,000 90 0.37 6. 3.0 0.98
1.23 -- -- -- -- -- -- 7. 4.0** 1.25 1.36 4500 15.1 -- -- -- -- 8.
5.5 1.17 -- 4290 26 -- -- -- 0.37 9. 7.0 1.63 1.46 4240 38 8,100
294,000 88 0.35 10. 10.0 1.55 1.59 3440 40 -- -- 86 0.25
__________________________________________________________________________
* Presented for comparative purposes, Styron a registered trademark
for The Dow Chemical Co. for polystyrene ** Polydiorganosiloxane as
described in Example 1.
From Table I, the polydiorganosiloxane modified polystyrene was
toughened as shown by an increase in impact strength (compression
molded) of more than 50 percent at a one weight percent level of
polydiorganosiloxane. The polydiorganosiloxane toughened
polystyrene as shown in Table I reaches the same level of toughness
between 2 and 3 weight percent polydiorganosiloxane (shown by
impact strength) as does the organic toughened polystyrene, Styron
T430, which contains about 6 to 8 weight percent of the organic
toughening additive. The tensile strength of the
polydiorganosiloxane toughened polystyrene is higher than the
Styron T430.
EXAMPLE 6
A hydroxyl endblocked polydiorganosiloxane having 20 mole percent
methylvinylsiloxane and 80 mole percent dimethylsiloxane and a
Williams plasticity of 0.067 inch was prepared by the emulsion
polymerization precedure as described in U.S. Pat. No. 3,294,725 by
polymerizer polydimethylsiloxane cyclic tetramer and
polymethylvinylsiloxane cyclic tetramer in an aqueous emulsion
using dodecylbenzene sulfonic acid as the superfactant. The
polydiorganosiloxane emulsion was 35 weight percent solids. The
following ingredients were mixed in a flask under a nitrogen
atmosphere and rapidly stirred at 40.degree.C. for 24 hours to
complete the emulsion polymerization. The emulsion was then cooled
and the emulsion was broken with calcium chloride. The resulting
polydiorganosiloxane modified styrene-acrylonitrile copolymer was
separated from the aqueous phase, washed twice with water and once
with ethanol and dried in a vacuum oven.
A. 128 grams of styrene, 64 grams of acrylonitrile 173.6 grams of
water 0.4 gram of K.sub.2 S.sub.2 O.sub.8 and 41.1 grams of the
polydiorganosiloxane emulsion containing 0.412 gram of
dodecylbenzene sulfonic acid.
B. for comparative purposes, this emulsion was prepared as
described above with the following ingredients:
128 grams of styrene, 64 grams of acrylonitrile, 144 grams of
water, 0.4 gram of K.sub.2 S.sub.2 O.sub.8 and 0.412 gram of
dodecylbenzene sulfonic acid.
The test samples were prepared as described in Example 4, A. The
notched Izod impact strength for A. was 0.690 foot-pounds per inch
of notch and for B., 0.492 foot-pounds per inch of notch. Thus, the
polydiorganosiloxane modified styrene-acrylonitrile showed an
increase in impact strength of about 40 percent over the unmodified
styrene-acrylonitrile copolymer.
EXAMPLE 7
Polydiorganosiloxane modified polystyrene compositions were
prepared and tested as described in Example 1 except 4 weight
percent polydiorganosiloxane was added and the molar ratio of the
siloxane units were varied as shown in Table II wherein the
polydiorganosiloxane is defined by m in the formula
HO{[(CH.sub.3).sub.2 SiO].sub.m [(CH.sub.3)(CH.sub.2 =
CH)SiO].sub.1.sub.-m }.sub.x H and x was such as to provide a
Williams plasticity greater than 0.060 inch.
TABLE II ______________________________________ Notched Izod Impact
Strength % Increase in Run. ft.-lbs./in. Impact Over No. m of Notch
Run No. 1 ______________________________________ 1. no polydi- 0.38
-- organo- siloxane 2. 0.905 0.37 -2.6 3. 0.820 1.25 +228.9 4.
0.770 1.01 +165.8 5. 0.700 0.42 +10.5
______________________________________
EXAMPLE 8
The polydiorganosiloxane modified polystyrene was prepared in
accordance with Example 1. A low temperature impact test was
carried out and consisted of enclosing mounted 3 inch by 0.5 inch
by 0.5 inch test bars in the notched Izod impact strength test in
an insulated environmental chamber which could be cooled to
-180.degree.C. by passing liquid nitrogen into the chamber. The
temperature was monitered with a thermocouple molded within the
test bars. The junction of the thermocouple was in the center of
the bars just below the notch. Prior experiments had shown
temperature differentials between the surface and center of the
test bars to be less than 1.degree.C. at temperatures as low as
-100.degree.C. provided that 10 minutes were allowed to come to
thermal equilibrium. The presence of the thermocouple was
demonstrated to have no detectable effect on the impact strength
values. After the mounted test specimen was brought to the desired
temperature, the chamber was quickly removed and the test bar was
impacted as the temperature was observed. The results were as shown
in Table III.
TABLE III ______________________________________ Notched Izod
Impact Strength, ft.-lbs./in. Temperature, .degree.C. of notch
______________________________________ 27.0 1.12 -6.0 0.80 -20.0
0.69 -41.5 0.82 -59.5 0.67 -76.0 0.67 -89.5 0.58 -105.5 0.24
______________________________________
The results show that the critical brittleductile transition was in
the range of -90.degree.C.
EXAMPLE 9
A. A mixture of 155 pounds of polydimethylsiloxane cyclics, 45.1
pounds of polymethylvinylsiloxane cyclics, 190 grams of a potassium
silanolate catalyst (sufficient to give 1 potassium atom per 10,000
silicon atoms) and 91 grams of dimethylformamide was polymerized at
130.degree. to 140.degree.C. for 3.5 hours under a nitrogen purge
with mixing action. At the end of the time, the reaction was
stopped with carbon dioxide. The resulting hydroxyl endblocked
polydiorganosiloxane had 19 mole percent methylvinylsiloxane units,
and 81 mole percent dimethylsiloxane units as determined by nuclear
magnetic resonance. The polydiorganosiloxane had a Williams
plasticity of 0.108 inch.
B. A portion of this was stripped in a commercial mixer for 1 hour
at 150.degree.C. under vacuum. The resulting polydiorganosiloxane
had a Williams plasticity of 0.126 inch.
C. A 150 gram sample of the polydiorganosiloxane obtained in A.
above was dried for 1 hour at 150.degree.C. under a nitrogen purge
in a commercial mixer. To the dried polydiorganosiloxane, 0.8 cc.
of the same potassium silanolate as used in A. above was added to
reactivate the polymerization. The polymerization was continued for
3.5 hours at 150.degree.C. under a nitrogen purge, stopped with
carbon dioxide and then stripped for 1 hour at 150.degree.C. under
vacuum. The resulting polydiorganosiloxane had a Williams
plasticity of 0.103 inch.
D. The procedure of C. was carried out on a 150 gram sample of the
polydiorganosiloxane obtained in A. above, except the
polymerization was continued for 24 hours. The resulting
polydiorganosiloxane had a Williams plasticity of 0.135 inch and
had 18 mole percent methylvinylsiloxane units and 82 mole percent
dimethylsiloxane units as determined by nuclear magnetic
resonance.
E. Each of the polydiorganosiloxanes from B., C. and D. above were
used to make polydiorganosiloxane modified polystyrene in
accordance with this invention. In each case, 36.76 grams of
polydiorganosiloxane was dissolved overnight in 919 grams of
styrene and then the mixture was bulk polymerized for 2.5 hours at
120.degree.C. The resulting mixture was cooled to 60.degree.C., 1.9
grams of benzoyl peroxide was added followed by a solution of 18
grams of sodium carboxymethylcellulose in 3100 ml. of water. The
mixture was stirred to make a suspension which was heated to
80.degree.C. overnight to complete the polymerization. Any
unreacted monomers were distilled from the suspension which was
then filtered, washed and dried to recover polydiorganosiloxane
modified polystyrene in the form of beads. The beads were
masticated in a Brabender Plasticorder (180.degree.C./6 minutes/62
r.p.m./CAM head) and compression molded at 177.degree.C. The
notched Izod impact strengths were determined and were as shown in
Table IV.
TABLE IV ______________________________________ Notched Izod Impact
Strength % Increase In Polydiorgano- ft.-lbs./in. Impact Strength
Siloxane of Notch Over Control
______________________________________ Control-none 0.38 -- B. 1.09
187 C. 0.93 145 D. 0.63 66
______________________________________
EXAMPLE 10
The polydiorganosiloxane modified polystyrene of Example 1 was
exposed to radiation from the carbon arc in an artificial
weathering apparatus, Dew Cycle Atlas Weatherometer*, for the times
shown in Table V. For comparative purposes, Styron T430 a high
impact polystyrene modified with 6 to 8 weight percent polydiene
was also run in the weatherometer. After the times shown, the
tensile strength and elongation at break and the notched Izod
impact strength were determined.
TABLE V
__________________________________________________________________________
Polydiorganosiloxane Modified Polystyrene Styron T-430
__________________________________________________________________________
Impact Strength, Impact Strength Time, Tensile, Elonga-
ft,-lbs./in. Tensile Elonga- ft.-lbs./in. Hours p.s.i. tion,% of
Notch p.s.i. tion,% of Notch
__________________________________________________________________________
0 4500 15.1 1.25 4020 29.3 1.09 16 4300 20.8 -- 4000 17.2 -- 36
4350 15.4 -- 4010 5.59 -- 72 4300 5.9 -- 3660 4.65 -- 107 4180 6.1
-- -- -- -- 110 -- -- -- -- -- 0.77 200 3680 6.2 1.04 -- -- 0.56
__________________________________________________________________________
EXAMPLE 11
A series of polydiorganosiloxane modified polystyrene compositions
were prepared by the procedure of Example 1 wherein the
polydiorganosiloxane had a Williams plasticity of 0.085 inch
instead of 0.071 inch and the initial bulk polymerization
temperature was varied. The polydiorganosiloxane modified
polystyrene compositions were isolated, compression molded and the
notched Izod impact strength determined. The gel fraction was also
determined by observing the weight fraction of insoluble material
in the polystyrene matrix. The insoluble weight fraction was
determined by dissolving a 10 gram portion of each composition in
methylene chloride and separating the gel fraction by
centrifugation, washing the gel fraction with methylene chloride
and then drying the gel. The results were as shown in Table VI.
TABLE VI ______________________________________ Initial Bulk
Polymeri- M.sub.n of zation Gel Soluble Impact Strength Temper-
Fraction, Poly- ft.-lbs./in. -ature, .degree.C. Wt. % styrene of
Notch ______________________________________ 80 3.2 162,000 0.52
100 19.9 169,000 0.77 120 16.6 116,000 1.07 140 13.6 102,000 1.18
______________________________________
EXAMPLE 12
A series of polydiorganosiloxane modified polystyrene compositions
were prepared by the procedure of Example 1, except the rate of
stirring was varied for each preparation. The resulting
polydiorganosiloxane modified polystyrene compositions were
isolated, notched Izod impact strengths were determined and
microtomed sections were examined by phase contract microscopy to
obtain the average particle sizes as shown by geometric mean
diameters (X.sub.g) of a log-normal particle size distribution. The
results were as shown in Table VII where S.sub.g is the standard
deviation factor.
TABLE VII ______________________________________ Impact Rate of
Strength, Stirring, ft.-lbs./in r.p.m. of Notch X.sub.g, .mu.M
S.sub. g ______________________________________ 40 1.10 0.47 1.81
80 0.70 -- -- 125 1.25 0.58 2.05 180 1.10 0.83 2.14 200 1.11 0.62
1.90 ______________________________________
EXAMPLE 13
This example is presented for comparative purposes.
A. A mixture of 70 grams of a commercial polystyrene (Styron 686)
and 2.1 grams of a hydroxyl endblocked polydiorganosiloxane having
19 mole percent methylvinylsiloxane units and 81 mole percent
dimethylsiloxane units and having a Williams plasticity of 0.139
inch, was mixed and sheared in a Brabender Plasticorder at
180.degree.C. for 15 minutes. The resulting non-uniform composition
was compression molded and the Izod impact strength was 0.37
foot-pounds per inch of notch.
B. The procedure in A. above was repeated except 0.7 grams of
dicumyl peroxide was added prior to mixing. The resulting
non-uniform composition was compression molded and the notched Izod
impact strength was 0.15 foot-pounds per inch of notch. As observed
both A. and B. showed no improvement in impact strength.
C. The polydiorganosiloxane as described in A. above was used to
prepare a polydiorganosiloxane modified polystyrene using the
procedure of Example 1. The resulting polydiorganosiloxane modified
polystyrene was isolated, compression molded and a notched Izod
impact strength of 1.09 foot-pounds per inch of notch was
obtained.
EXAMPLE 14
This example shows the effect of cold rolling on the mechanical
properties of the polydiorganosiloxane modified polystyrene
compared to the commercial polybutadiene modified polystyrene
(Styron T-430 ). In Table VIII, Composition A. was Styron T-430,
Composition B. was the polydiorganosiloxane modified polystyrene of
Example 5, Run No. 5 and Composition C. was a polydiorganosiloxane
modified polystyrene prepared as described in Example 1. Each
material was injection molded into tensile bars 5.25 inch by 0.5
inch by 0.135 inch and passed through a variable speed rubber mill
at room temperature with both rolls set at 34 r.p.m. and with the
original gap set at 0.135 inch and then the gap was decreased in
0.005 inch increments after each pass. The mechanical properties
were as shown in Table VIII.
TABLE VIII
__________________________________________________________________________
Tensile Strength, p.s.i. Elongation, % Impact Initial Strength,
Compression, Modulus, ft.-lbs./in. Composition % At Yield At Break
At Yield At Break p.s.i. of Notch
__________________________________________________________________________
A. 0 4000 4050 5 20 101,000 1.00 15.1 4200 4890 6 23 90,500 -- 30.5
5370 5820 6 14 99,200 -- 44.6 6600 6600 8 31 93,200 -- B. 0 5100
5250 6 16 106,500 0.99 12.7 6450 6530 7 12 112,000 -- 31.3 7700
7060 7 16 111,000 -- 42.5 7860 6960 9 22 104,000 1.34 C. 0 4524
4890 5 26 119,000 1.40 15.8 4670 5550 5 34 100,000 -- 27.8 6240
6040 7 44.4 96,000 -- 42.9 7120 6540* 8 153* 104,000 1.66
__________________________________________________________________________
*Sample did not fail, test discontinued at this point.
* * * * *